Polishing formulations for the chemical mechanical planarization (CMP) of integrated circuit wafers, as well as polishing compounds for high technology optical components typically consist of an aqueous dispersion of solids (the abrasives) combined with a variety of chemical constituents. Such commercial materials typically are sold in several parts, one containing the abrasive component in a concentrated form and the other part containing the chemical component(s) in a concentrated form. As the technology of CMP polishing has become more critical, complex chemical and abrasive systems have been developed. These aqueous formulations must exhibit long shelf life, and good stability so that the materials do not change while in storage, thus becoming useless for their intended purpose. For example, if a dispersion of solids is stored and the solids settle in the container to a hard or difficult to mix sediment, the dispersion is no longer readily usable by the customer.
Many attempts to make one component systems in which the chemical as well as the abrasive components are mixed in one liquid system have proven problematic. The problems occur because the presence of the chemical constituents is rarely conducive to forming stable solid dispersions, consequently the solids settle to the bottom of the container and require subsequent redispersion prior to use. This presents many problems to the end user. If the solids have settled into a difficult to redisperse sludge, the chances of utilizing all of the settled material are not good because it will stick to the container. Furthermore, shaking or stirring a large container such as a drum or tote is impractical.
The ideal concept would be to make a slurry exactly as the final end user would use it, and then "freeze it in time" so that it will be exactly as the end user wants it, three or even six months after the slurry is made. Since the main reason for instability is due to the aqueous dispersions that these slurries are sold as, it would be reasonable to assume that if one could eliminate the "aqueous" part of the system, the stability issues for both the chemical and abrasive constituents would be minimized.